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Abstract:

A process for producing biodiesel from natural oils and/or fats, a low
molecular weight C1-C6 alcohol and catalyst is described. The
process preferably uses vegetable oils and is specifically configured for
producing biodiesel from castor oil.

Claims:

1. A process for producing biodiesel from natural oils and/or fats in the
presence of a low molecular weight alcohol and a catalyst, comprising the
following steps of reaction ((a) to (e)) and purification ((f) to (g)):a)
directing, under process conditions of temperature from ambient
temperature to 140.degree. C., pressure from atmospheric pressure to 10
bars and a molar ratio of alcohol/(oil or fat) of 3 to 30, oil or fat
(1), alcohol (2) and catalyst (3), to a first reaction module (MR-1A), to
mix, react, and separate a first dense phase (5), and a first light phase
(4), formed during the reaction;b) directing oil or fat (12) and alcohol
(13) to a second reaction module (MR-1B), together with a fraction (11)
containing residual catalyst from the other reaction modules (MR-1A and
MR-2), mixing and reacting said oil or fat (11), said alcohol (12) and
said fraction (13) under reaction conditions preferably similar to those
in the first reaction module (MR-1A), and after the required reaction
period separating the resulting product into a second dense phase (15)
and a second light phase (8);c) directing the first and second light
phases (4 and 8) to a third reaction module (MR-2), together with alcohol
(6) and catalyst (7), reacting them tinder reaction conditions preferably
similar to those of the first reaction module (MR-1A), and after the
required reaction period separating the resulting products into a third
dense phase (9) and a third light phase (10);d) directing the third light
phase (10) leaving the third reaction module (MR-2), sent as a phase
(23), to a purification system (SP-1);e) directing the second dense phase
(15) separated in the second reaction module (MR-1B) and the excess, if
any, of other dense phases (14), to a recovery system (SREC-1);f)
directing the third light phase (23) arriving at the purification system
(SP-1) to a neutralization system (SN-1) where it reacts with a
neutralizing agent (16), and then separating the resulting product into a
fourth dense phase (17), which is directed to a recovery system (SREC-1)
and a fourth light phase (18), which is directed to a washing system
(SLAV-1);g) removing water-soluble contaminants present in the light
phase in the washing system (SLAV-1), with the help of water (37);h)
separating a fifth light phase (19) which leaves the washing system
(SLAV-1), and directing it to a drying and wax removal system (SSRC-1),
to obtain said biodiesel (21), and preferably directing separated aqueous
phase (20) to the recovery system (SREC-1).

2. A process according to claim L alternatively comprising the following
reaction steps (a) to (g):a) directing, under process conditions of
temperature from ambient temperature to 140.degree. C., pressure from
atmospheric pressure to 10 bars and a molar ratio of alcohol/(oil or fat)
from 3 to 30, oil or fat (1), alcohol (2) and catalyst (3), to a first
reaction module (MR-1A), to mix, react, and separate a first dense phase
(5), and a first light phase (4), formed during the reaction;b) directing
oil or fat (12) and alcohol (13) to a second reaction module (MR-1B),
together with a fraction (11) containing residual catalyst, from the
other reaction modules (MR-1A and MR-2), mixing and reacting said oil or
fat (11), said alcohol (12), and said fraction (13) under reaction
conditions preferably similar to those in the first reaction module
(MR-1A), and after the required reaction period separating the resulting
product into a second dense phase (15) and a second light phase (8);e)
directing the first and second light phases (4 and 8) to a third reaction
module (MR-2), together with alcohol (6) and catalyst (7), mixing and
reacting them under reaction conditions preferably similar to those of
the first reaction module (MR-1A), and after the required period
separating the resulting products into a third dense phase (9) and a
third light phase (10);d) directing the third light phase (10), the
second dense phase (15) from the second reaction module (MR-1B) and a
recycled dense phase (29) to a catalyst extraction system (SEXT-1), to
obtain a fourth dense phase (28) and a fourth light phase (23);e)
directing the fourth light phase (23) to a purification system (SP-1);f)
directing one part, of the fourth dense phase (28) to form a recycled
dense phase (29) for the catalyst extraction system (SEXT-1), a second
part to form a fifth dense phase (38) containing residual catalyst, and
the remainder (30) to a recovery system (SREC-1);g) directing any excess
from the dense phases to the recovery system (SREC-1).

3. A process according to claim 2, additionally comprising the following
alternative reaction steps:a) passing the second dense phase (15, 31)
through an alcohol evaporation/distillation system (SEVAP-2) and then
directing a liquid phase (32) to a catalyst extraction system (SEXT-1);b)
directing alcohol removed (33) to a recovery system (SREC-1).

4. A process according to claim 1, comprising the following alternative
purification steps:a) directing the third light phase (23) to a
neutralization system (SN-1), where it reacts with a neutralizing agent
(16), and then separating the resulting products into a fourth dense
phase (17) and a fourth light phase (18);b) directing the fourth light
phase (18), to an alcohol extraction system (SEXT-2), and the fourth
dense phase (17) to a recovery system (SREC-1);c) promoting in the
alcohol extraction system (SEXT-2), with the aid of recovered glycerine
(35), extraction of part of the excess alcohol retained in the fourth
light phase (18), to prevent hydration of this alcohol by contact with
water from the washing system (SLAV-1), thereby obtaining and separating
a fifth dense phase (36), which is sent to a recovery system (SREC-1) to
recover anhydrous or semi-anhydrous alcohol, and a fifth light phase
(34);d) directing the fifth light phase (34) to a washing system
(SLAV-1), which also receives water (37), in order to remove
water-soluble contaminants in said fifth light phase, and separating the
resulting product into an aqueous phase (20), which is directed to a
recovery system (SREC-1), and a sixth light phase (19);e) directing the
sixth light phase (19) to a drying and wax removal system (SSRC-1), from
which said biodiesel (21) is recovered.

5. A process according to claim 1 comprising the following purification
steps:a) directing the third light phase (23) to an alcohol extraction
system (SEXT-2), which also receives recovered glycerine (35) from a
recovery system. (SREC-1), to promote extraction of part of the excess
alcohol retained in the third light phase (23), to prevent hydration of
the alcohol by contact with water from the washing system (SLAV-1),
thereby obtaining a fourth dense phase (36) and a fourth, light phase
(34);b) separating and directing the fourth dense phase (36) to a
recovery system (SREC-1) to recover anhydrous or semi-anhydrous
alcohol;c) directing the fourth light phase (34) to a neutralisation
system (SN-1) to react with a neutralizing agent (16), and then
separating the resulting products into a fifth dense phase (17), which is
directed to a recovery system (SREC-1), and a fifth light phase (18);d)
directing the fifth light phase (18) to a washing system. (SLAV-1), which
also receives water (37), in order to remove water-soluble contaminants
in said fifth light phase, and separating the resulting product into a
sixth dense aqueous phase (20), which is directed to a recovery system
(SREC-1), and a sixth light phase (19);e) directing the sixth light phase
(19) to a drying and wax removal system (SSRC-1), from which said
biodiesel (21) is recovered.

6. A process according to claim 1, wherein alternatively, before washing
in a washing system (SLAV-1), a neutralised light phase (24) is submitted
to an additional step of evaporation or distillation of excess alcohol,
wherein said step includes directing said light phase to an
evaporation/distillation system (SEVAP-1) to remove part or all of the
residual alcohol content, separating and directing the alcohol removed
(27) and a dense phase (26) to a recovery system (SREC-1), while a light
phase (25) is sent to a washing system, (SLAV-1).

7. A process according to claim 1, wherein any dense phase (15, 17, 20,
22, 26, 27 and/or 36) arriving at the recover/system (SREC-1) enters this
system at specific points in accordance with the contents of water
therein and the decision to be adopted as to type of recovery.

8. A process according to claim 7, wherein the type of recovery involves
premixing of the fractions or, alternatively separate treatment of the
aqueous fractions, recovering all of the glycerine from the aqueous
fractions or only treating them for disposal, converting the soaps in
fatty acids and recovering the fatty acids or otherwise, and/or
dehydrating the recovered alcohol or offering it for sale as hydrated
alcohol (when the process uses ethyl alcohol), or any other combination.

10. A process according to claim 1, wherein the alcohol is a pure
C1-C6 alcohol or a mixture thereof.

11. A process according to claim 1, wherein the alcohol is pure methanol
or ethanol or a mixture thereof.

12. A process according to claim 1, wherein die molar ratio of
alcohol/(oil or fat) is between 4 and 15.

13. A process according to claim 1, wherein the catalyst is an acid or
basic catalyst.

14. A process according to claim 13, wherein die proportion of basic
catalyst to oil or fat is 0.1 to 2.5% by weight relative to the weight of
oil or fat starting material in die unit.

15. A process according to claim 1,wherein if a basic catalyst is used for
the transesterification reaction, the neutralizing agent can be any
organic or inorganic acid, strong or weak, concentrated or dilute, in
aqueous or alcoholic solution, as long as the turning point of the
neutralization of the catalyst is carefully controlled.

16. A process according to claim 15, wherein the acids are preferably
hydrochloric, sulphuric, phosphoric, acetic and citric acids.

17. A process according to claim 15, wherein acidic buffers in the desired
pH range can optionally be used in order to facilitate control.

18. A process according to claim 1, wherein if a basic catalyst is used in
the transesterification reaction, the water for washing is pure or with
pH controlled in the range between 1 to 7, and preferably between 3 and
5.

19. A process according to claim 18, wherein the pH of the water for
washing is controlled in the range between 3 and 7.

20. A process according to claim 1, which includes three reaction steps,
two reaction steps in parallel (R-1A and R-1B) using oil or fat as a
starting material, and one reaction step in series (R-2) using as a
starting material the light phases produced in the earlier reaction steps
(R-1A and R-1B).

21. A process according to claim 20, wherein one of the two initial steps
CR-1B) reuses the catalyst used in the other steps.

22. A process according to claim 21, wherein the reuse of the catalyst is
accomplished by means of a fraction (11) which comprises totally or
partially of first and third dense phases (5 and 9) separated in first
and third reaction modules (MR-1A and MR-2).

[0002]The transesterification of vegetable oils to produce fatty acid
esters is an ancient process with a broad range of industrial uses. In
the 1980s and 1990s, this process was adapted for the production of an
alternative fuel to diesel. The basic requirements of the new processes
are high purity and yield. These objectives have been fully achieved, but
only when the raw materials are methanol and non-hydroxylated vegetable
oils, with rapeseed and soybean oil being the most used.

[0003]In Brazil, due to regional peculiarities, there is considerable
government interest in developing a specific process for the production
of biodiesel from castor oil. However, since this oil possesses
particular characteristics due to the presence of a hydroxyl group in its
molecular structure, the conventional processes do not produce good
results. This has necessitated research and development of a process
specially adapted to the transesterification of castor oil.

[0004]Additionally, in Brazil there is also enormous interest in replacing
methanol with ethanol, which introduces great complexity into the
process, especially when the oil selected for the transesterification
reaction is castor oil, due to the fact that both raw materials have
hydroxyl groups in their molecular structures. Moreover, ethanol is not
used in any industrial biodiesel plant outside Brazil, and in no high
capacity plant, even in Brazil.

[0005]U.S. Pat. No. 4,608,202 describes a process for producing fatty acid
esters of short-chain aliphatic alcohols by catalytic transesterification
of natural fats and/or oils containing free fatty acids (oil phase), with
the corresponding monoalcohols. The oil phase is submitted to preliminary
esterification with the monoalcohols in the presence of acid
esterification catalysts at a temperature no greater than 120° C.
under pressures no greater than 5 bars and in the presence of a liquid
entraining agent substantially immiscible with the oil phase, after which
the reaction product is separated into an entraining agent phase
containing the acid catalyst and water of reaction and the treated oil
phase, the oil phase is subjected to trans-esterification while the
acidic catalyst-containing entraining agent phase is returned, after
partial drying, to the preliminary esterification step. By this process,
fats and/or oils with acid numbers of up to 60 can be processed in the
preliminary esterification step to give an oil phase having a low acid
number.

[0006]U.S. Pat. No. 4,652,406 discloses producing fatty acid esters by
catalytic esterification of natural oils and fats. Initially the free
fatty acids are reacted, for example, with methanol in the presence of an
acid catalyst at 50-120° C. and atmospheric pressure. The
resulting mixture separates in two phases: (1) an alcoholic phase
containing the acid catalyst and part of the water of reaction; and (2)
an oil phase. The phases are recovered separately. The oil phase is then
extracted with an extractant, preferably immiscible, which comprises a
mixture of glycerol and methanol, to remove the residual water of
reaction. In the final step, the extracted oil phase is transesterified
with a C1-C4 alkanol, in the presence of an alkaline catalyst
at substantially atmospheric pressure.

[0007]U.S. Pat. No. 4,695,411 discloses a process for preparing a
composition of fatty acid esters useful for diesel engines, wherein the
composition contains at least one hydrated ethyl alcohol. Step (A)
consists of acid transesterification in the presence of a hydrated
alcohol such as ethyl alcohol containing 1 to 60% by weight of water,
producing glycerol and ethyl esters; step (B) consists of reducing the
free acidity of the ester phase, and step (C), the basic esterification
of the phase resulting from phase B in the presence of a monoalcohol with
1 to 5 carbon atoms, and recovery of the ester phase.

[0008]U.S. Pat. No. 5,354,878 discloses a process for producing higher
fatty acid alkyl esters from an oil phase and lower alcohols by catalytic
esterification at temperatures up to 100° C. in the presence of an
alkaline catalyst, which includes: a) introducing a mixture of oil phase,
alcohol and catalyst at reaction temperature into the top of a first
reactor column, at a rate of flow which is lower than the rate of
separation of glycerine from the reaction mixture; b) passing the
reaction mixture to a second reactor for additional transesterification;
c) the reaction mixture thus obtained is additionally freed of glycerine
in an initial separation step by a short duration wash; d) the reaction
mixture is passed to a third reactor with additional alcohol and
catalyst, and at a flow rate conforming to the first step of the process;
e) the reaction mixture is additionally transesterified; f) the reaction
product is freed from the remaining methanol, glycerine, the soaps formed
and catalyst in a second separation step, through the addition of an
aqueous extraction buffer solution; and g) the reaction mixture is freed
of primary alcohols by rectification, washed with suitable extraction and
washing solutions, and dried.

[0009]U.S. Pat. No. 5,434,279 discloses a process for esterification in
various steps for oils and fats, including oils used such as those for
frying, which comprises of the addition, after the second step is
finished, of at least part of the glycerine from the first step; the
glycerine is separated again, and the fatty acid ester is separated from
the excess alcohol or diol and acidified. It is claimed that the process
results in a highly pure fatty acid ester.

[0010]Brazilian Application PI0404243-3A discloses a process for producing
biodiesel from semi-refined vegetable oil, anhydrous alcohol and an
alkaline catalyst. The process is in two steps, with a temperature of
60-80° C. The reagents are mixed in a first reactor, and after
allowing time for reaction the products formed are sent to a first
evaporator to separate the non-reacted alcohol, with the alcohol being
recovered in a condenser. The residues of oil, biodiesel and glycerine
are cooled and sent to a first centrifugal separator for separation,
under an inert atmosphere, of the glycerine from the residual oil and
biodiesel. The biodiesel formed and the residual oil are then reacted
with more anhydrous alcohol and alkaline catalyst by mixing in a second
continuous mixer. After mixing, the mixture is heated and passed to a
second reactor, where the reaction occurs, and the product then receives
a dose of hydrochloric or sulphuric acid to deactivate the alkaline
catalyst; the alcohol is separated in an evaporator, and the product
proceeds to a second centrifuge for separation of the glycerine and
biodiesel. The product is washed in water lightly acidified with citric
acid in sufficient quantity to react with residual soaps, and the washing
water then separated in a washing centrifuge. The washed biodiesel is
sent to a vacuum dryer, cooled and then stored. Certain aspects of the
technology described in this Brazilian application could affect the
economic viability of the same. Moreover, the process is not designed for
the specific features of castor oil.

[0011]In general, the processes used worldwide in industrial plants for
producing biodiesel were not developed for use with castor oil and/or
have not even been tested, or simply do not work with this raw material.

[0012]The processes described in the scientific literature and in patents
either do not use recycling or merely recycle the dense phase from the
final reaction step to the first reaction step, or they react the ester
phase from the second reaction step with part of the glycerine from the
first reaction step. The steps of the reaction are sequential, that is
the product of the first step is the starting material of the second,
with the possibility of a further step, also sequential. By contrast, the
reaction flow proposed in this invention uses `parallel` steps, optimizes
recycling flow, and allows better re-utilization of the residual
catalyst, minimizing consumption of the catalyst.

[0013]Another distinctive aspect of the invention is the fact that the
processes of the state of the art mix the dense phases from the reactions
with the aqueous phases from washing. Subsequently, after neutralizing
the excess catalyst and recovering the residual alcohol, the water has to
be evaporated off in order to concentrate the glycerine to 85%. The
present invention, on the other hand, establishes technical conditions
that allow the aqueous fractions to be processed separately, whenever it
is economically advantageous to do so. Such flexibility also makes it
possible to limit the treatment to the minimum necessary for the disposal
of the aqueous effluents, if the level of glycerine or of alcohols
(depending on the method chosen for alcohol recovery) does not
economically justify the costs of the treatment. Opting for separate
treatment enables the removal of a large part of the glycerine produced
in the form of a highly concentrated fraction that requires only
distillation of the residual alcohol and neutralization of excess
catalyst (not necessarily in this order), which is minimized in the
present process. The soap may or may not be converted into fatty acid,
depending only on the existence of a local market for the fatty acids.
Due to the fact that these glycerine fractions contain less soap and
catalyst, the final level of saline impurities in the glycerine product
is also lower.

[0014]The industrial processes most used in the art for biodiesel
production use steps of neutralization, washing with water and vacuum
drying for purifying the final product. The proposed process, however,
presents an alternative use for one of the dense phase fractions
generated in the process itself to increase the recovery of catalyst by
returning part of this fraction to the process. Although the aim is to
minimize the consumption of catalyst, the process of the invention also
reduces the level of contaminants in the crude biodiesel fraction,
facilitating the washing process and reducing the consumption of water
and acid used in neutralization.

[0015]In addition, the present invention also presents an alternative use
of glycerine to extract a large part of the excess alcohol before the
step of washing the biodiesel, and later recovery by evaporation of the
alcohol absorbed in the glycerine. This alternative is particularly
interesting when the alcohol used in the transesterification is ethanol,
since it minimizes the water content of the recovered alcohol and the
cost of dehydration.

[0016]Therefore, there is still a need in the art for a process for
obtaining biodiesel by transesterification of natural oils and/or fats
and, more specifically, of castor oil, in the presence of a
transesterification catalyst, wherein this process includes a step (a) in
which virgin and/or recycled oil and/or fat are/is made to react with a
low molecular weight primary alcohol and a catalyst, followed by (b)
separation of the dense phase produced during step (a), containing a high
glycerine content, a step (c) in which the reactants are virgin and/or
recycled oil/fat, the low molecular weight primary alcohol and the dense
phases separated in steps (b) and (f) plus part of the dense phase
resulting from the extraction carried out in step (g), followed by (d)
separation of the dense phase produced during step (c), with a high
glycerine content (added plus produced), a step (e) in which the
reactants are the light phases obtained after separation in steps (b) and
(d), the low molecular weight primary alcohol and the transesterification
catalyst, followed by (f) separation of the dense phase produced during
step (e), with a high glycerine content, and an alternate step (g) of
extracting the excess catalyst contained in the light phase obtained
after separation in step (f), through contact with the dense phase
separated in step (d), and additional steps for purification and
finishing, as well as treatment of effluents and recovery of glycerine,
alcohol and fatty acids, with flexibility to suit the economics of the
recovery process to the various kinds of raw materials, alcohols and
catalysts, and including options to minimize the moisture content of the
recovered alcohol, and such a process is described and claimed in the
present application.

SUMMARY OF THE INVENTION

[0017]Broadly speaking, the process of the invention for producing
biodiesel from natural oils and/or fats in the presence of a
transesterification catalyst includes various processing steps, which to
facilitate understanding can be grouped into three distinct sections: a
Reaction Section, in which the transesterification reactions take place;
a Purification Section, where the impurities resulting from the
production process are removed; and a Section for Recovering Alcohols,
Glycerine and Fatty Acids. In the Reaction Section, the following steps
of the process are carried out: [0018]a) First reaction step (MR-1A),
in which the reactants are virgin and/or recycled oil and/or fat, a low
molecular weight primary alcohol and a transesterification catalyst,
giving fatty acid esters and glycerine; [0019]b) Separation of the dense
phase produced during step (a), this phase having a high glycerine
content and a very low water content; [0020]c) New initial reaction step
(MR-1B), in which the reactants are virgin and/or recycled oil and/or
fat, a low molecular weight primary alcohol and the dense phases
(previously submitted to separation of solids) produced in reaction steps
MR-1A and MR-2, and, optionally part of the dense phase resulting from
the extraction operation in step (g); [0021]d) Separation of the dense
phase produced during step (c), which has a high glycerine content;
[0022]e) Second reaction step (MR-2), in which the reactants are the
light phases of reaction steps MR-1A and MR-1B, a low molecular weight
primary alcohol and a transesterification catalyst; [0023]f) Separation
of the dense phase produced during step (e), which has a high glycerine
content and a very low water content; [0024]g) Alternatively, extraction
of the residual catalyst contained in the light phase of reaction step
MR-2, through contact with the dense phase separated from reaction step
MR-1B, the dense phase having previously been submitted to the
evaporation of excess alcohol, or otherwise; [0025]h) Neutralization of
the remaining dense phase fractions; and [0026]i) Evaporation of the
excess alcohol, especially from the fraction separated in step (d),
whereby a product with a high concentration of glycerine is obtained, and
levels of contaminants lower than those produced in the processes of the
state of the art for homogenous catalysis.

[0027]The crude biodiesel produced is then sent to the Purification
Section, where it is submitted to a process of purification and finishing
that comprises: [0028]a) When the catalyst used is of the basic type,
an optional step of partial or total neutralization of the residual
alkalinity in the biodiesel from steps (f) and (g) in the Reaction
Section, by adding acidified or pure water, followed by separation of the
resulting dense phase; [0029]b) Various stages of washing of the
biodiesel fraction from step (a) with pure water or in counter current,
until complete removal of residual contaminants soluble in water, such as
soaps, salts, glycerine and alcohols; [0030]c) Drying of the washed
biodiesel fraction; and [0031]d) Depending on the oil or fat used as raw
material, removal of waxes and other substances separable by cooling, to
suit the plugging point to local specifications.

[0032]A second alternative for the purification and finishing of the
biodiesel comprises the following steps: [0033]a) When a basic-type
catalyst is used, neutralization of the residual alkalinity in the
biodiesel from steps (f) or (g) in the Reaction Section, through the
controlled addition of an alcoholic solution of an acid, which
preferably, but not necessarily, has a low ionization constant; [0034]b)
Distillation or total or partial evaporation of the alcohol contained in
the biodiesel fraction, followed by separation of the resulting dense
phase; [0035]c) Washing of the biodiesel fraction from step (b) with pure
water or in counter current, until the complete elimination of the
residual water-soluble contaminants, such as soaps, salts, glycerine and
alcohols; [0036]d) Drying of the washed biodiesel fraction; and [0037]e)
Depending on the oil or fat used as raw material, removal of waxes and
other substances separable by cooling, to suit the plugging point to
local specifications.

[0038]A third alternative for the Purification Section involves
purification and finishing of biodiesel produced by means of any reaction
configuration, either a conventional configuration or those of the
present invention, but especially for biodiesel produced with ethanol,
which can be carried out via the following steps: [0039]a) When a
basic-type catalyst is used, neutralization of the residual alkalinity in
the biodiesel from steps (f) or (g) in the Reaction Section, by means of
the controlled addition of an alcoholic solution of an acid, preferably,
but not necessarily, of a low ionization constant; [0040]b) Before or
after the neutralization of the biodiesel described in step (a) above,
extraction of the excess alcohol with a pre-evaporated glycerine fraction
(low level of alcohol), in order to minimize or eliminate a later step of
evaporating the alcohol in the biodiesel. A glycerine phase enriched with
alcohol is forwarded to a special alcohol recovery section, by means of
evaporation or distillation under conditions that favour minimization of
the water content in the recovered alcohol. The glycerine is then either
totally or partially returned to the extraction system; [0041]c)
Optionally, evaporation/distillation of the residual alcohol still
contained in the biodiesel fraction, followed by physical separation of
the resulting dense phase; [0042]d) Washing of the biodiesel fraction
resulting from step (a), (b) or (c), according to the sequence chosen,
with pure water or in counter current, until the complete elimination of
the residual water-soluble contaminants, such as soaps, salts, glycerine
and alcohols; [0043]e) Drying of the washed biodiesel fraction; and
[0044]f) Depending on the oil or fat used as raw material, removal of the
waxes and other substances by cooling, to suit the plugging point to
local specifications.

[0045]The dense phases separated in the Reaction and Purification
Sections, containing glycerine, alcohols, catalyst residues, soaps and
salts, are forwarded to the Recovery Section for Alcohols, Glycerine and
Fatty Acids, where these products are recovered, in accordance with the
economic benefits of the process, which in turn depend on the local
market value for these products.

[0046]The present invention offers flexibility, depending on economic
conditions and the type of raw material (oil or fat, alcohol and
catalyst) used, for various alternative structures for the steps in the
Recovery Section for Alcohols, Glycerine and Fatty Acids. Thus,
glycerine-rich fractions can be treated together with the water-rich
fractions, or not; fatty acids can be recovered or not; the aqueous
fractions can go through the recovery steps or be treated only for
disposal purposes, etc.

[0047]Within the many possibilities, some basic steps are described below,
not necessarily in order of sequence: [0048]a) Neutralization of excess
catalyst; [0049]b) Recovery of residual alcohols by
evaporation/-distillation; [0050]c) Acidification, to transform soaps
into fatty acids, with subsequent separation of the light phase, rich in
fatty acids; and [0051]d) Neutralization of the glycerine-rich phase and
concentration of the glycerine to the desired concentration by
evaporating excess water.

[0052]With the option of recovering glycerine from the aqueous fractions,
disposal of aqueous effluents becomes minimal or non-existent, due to the
recovery of the water used for washing during the glycerine concentration
phase.

[0053]The invention thus offers a process for producing biodiesel by
transesterification of natural oils and/or fats wherein use is made of
dense phase fractions produced within the process itself in order to
minimize catalyst consumption.

[0054]The invention also offers a process for producing biodiesel by
transesterification of natural oils and/or fats which offers a reduction
in the level of contaminants in the crude biodiesel fraction,
facilitating the purification process and reducing the consumption of
water and acid used for neutralization.

[0055]In addition the invention offers a process for producing biodiesel
by transesterification of natural oils and/or fats, wherein a highly
concentrated glycerine fraction is obtained, exceeding the specifications
for crude glycerine, containing less soap and catalyst, with an equally
minimized final level of salt impurities.

[0056]The invention also offers a process for recovering excess alcohol
(used for biodiesel production) with a low water content, reducing the
cost of reusing the same.

[0057]The invention also offers a process which allows for flexibility in
deciding to what extent it is advantageous to recover residual quantities
of glycerine and alcohols contained in the washing effluents, minimizing
consumption of energy and the cost of treating aqueous effluents.

BRIEF DESCRIPTION OF THE DRAWINGS

[0058]FIG. 1, attached, is a flow diagram showing a first alternative
configuration of the process of the invention, considering continuous
operation.

[0059]FIG. 2, attached, is a flow chart showing an alternative
configuration for the process of the invention, with one or two
additional stages to increase recovery of the catalyst and/or alcohol.

[0060]FIGS. 3 and 4, attached, are flow diagrams showing alternative
configurations of the process for the biodiesel purification steps,
applicable to any reaction configuration, either a conventional
configuration or those of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0061]The invention discloses a process for producing biodiesel from
vegetable oils and animal fats, typically castor oil, and low molecular
weight alcohols in the presence of a transesterification catalyst,
typically acidic or basic, by suitable combination of a series of single
operations, operational conditions and process design.

[0062]The process comprises three reaction steps, two of them in parallel,
(R-1A) and (R-1B), using oil as the starting material and one in series
(R-2) which uses as starting material the biodiesel-rich phases generated
in the previous steps, (R-1A) and (R-1B). In addition, one of the two
first two reaction steps, (R-1B), reuses the catalyst used in the other
steps.

[0064]The ideal temperate, pressure and proportion of reactants will
depend on the fatty acid composition in the raw materials used. For
example, castor oil which contains from 85 to 90% wt of ricinoleic acid
requires specific conditions of reaction as a function of the specific
physical chemical properties of castor oil.

[0065]The castor or other vegetable oil or animal fat used should
preferably have a free fatty acid content of less than 5% wt, more
preferably less than 0.5% wt, and most preferably less than 0.1% wt, and
preferably an acid value less than 10 mg KOH/g, more preferably less than
1 mg KOH/g and most preferably less than 0.2 mg KOH/g.

[0066]The moisture content of the oil or fat should preferably be less
than 0.8% wt, more preferably less than 0.2% wt and most preferably less
than 0.1% wt.

[0067]The catalyst may be either of the acid or basic type, but is
preferably of the basic type and more preferably constituted by sodium or
potassium hydroxide or by sodium or potassium methoxide or sodium or
potassium ethoxide; and it is preferably used in the proportion of 0.1%
to 2.5% by weight relative to the oil or fat.

[0068]If a basic catalyst is used in the trans-esterification reaction,
the neutralizing agent can be any organic or inorganic acid, strong or
weak, concentrated or dilute, aqueous or alcoholic, provided that the
turning point of neutralization of the catalyst is carefully controlled.
Optionally, to facilitate control, acid buffers in the desired pH range
can be used. The acids preferably comprise hydrochloric, sulphuric,
phosphoric, acetic and/or citric acid.

[0069]The low molecular weight primary alcohol is an alcohol in the range
C1-C6. The most preferred is ethyl or methyl alcohol, used in
the proportions indicated above. The process also allows the use of
mixtures of alcohols, provided that the molar ratios (mixture of low
molecular weight alcohols/vegetable oil or animal fat) are maintained as
specified.

[0070]The preferred embodiments of the invention will be described below
with reference to the attached drawings.

[0071]It should be made clear that the drawings do not indicate all of the
possible arrangements of the process covered by the present invention.

[0072]In FIG. 1, the reaction modules (MR-1A), (MR-1B), and (MR-2) are
sets of equipment which function, at least, as mixers, reactors,
separators, heat exchangers and pumps; the present invention is not
limited to any particular models for these items of equipment.

[0073]For a better understanding and description of the process, the flow
diagram in FIG. 1 can be divided into two sections: a Reaction Section
(SR-1) and a Purification Section (SP-1). The starting materials for the
process, comprising oil or fat (1), alcohol (2) and catalyst (3), are fed
to reaction module (MR-1A), in the ideal proportions and at the ideal
temperatures for the type of raw materials used. As they pass through the
reaction module (MR-1A) these materials are mixed, reacted and separated
into a dense phase (5) and a light phase (4) both formed during the
reaction.

[0074]Simultaneously, fresh oil or fat (12) and alcohol (13) are fed to a
reaction module (MR-1B), to which is also fed a fraction (11) constituted
totally or partially of the dense phases (5) and (9) separated in the
reaction modules (MR-1A) and (MR-2).

[0075]The three are supplied to the reaction module (MR-1B), regulated to
the ideal proportions and temperature, and mixed, reacted, and separated
into a dense phase, (15), and a light phase, (8), both formed during the
reaction.

[0076]The light phases separated in reaction modules (MR-1A), (4), and
(MR-1B), (8), are forwarded to reaction module (MR-2), together with
fresh alcohol (6) and catalyst (7). These four, previously regulated to
the ideal proportions and temperature, are mixed, reacted, and separated
into a dense phase (9) and light phase (10), formed during the reaction.

[0077]The totality of the light phase (10) thus separated, constituted by
biodiesel, excess alcohol and catalyst, soaps and impurities, is sent as
(10) and (23) to the Purification Section (SP-1).

[0078]The dense phase separated in reaction module (MR-2) is withdrawn as
(9), and is united with the dense phase (5) separated in reaction module
(MR-1A) to give (11), which is fed to reaction module (MR-1B). This
fraction (11) enables the catalyst to be reused. The dense phase (15)
separated in reaction module (MR-1B), (15), and the excess (if any) of
the other dense phases (14) pass to the Section for Recovering Alcohols,
Glycerine and Fatty Acids (SREC-1).

[0079]In the Purification Section (SP-1), the light phase (23) is
forwarded to a neutralization system (SN-1), where it is subjected to
reaction with a neutralizing agent (16) and separation of the dense phase
(17) and light phase (18) products of neutralization. The light phase,
still constituted by crude, but neutralized, biodiesel, passes to the
washing system (SLAV-1) as (18) and the dense phase (17) is sent to the
Section for Recovering Alcohols, Glycerine and Fatty Acids (SREC-1).

[0080]The washing system (SLAV-1) also receives fresh water (37), the
function of which is to remove water-soluble contaminants in the
biodiesel, such as soaps, salts, alcohols, catalyst residues and
glycerine. After close contact of the two currents, counter current or
otherwise, for various stages, the biodiesel is separated as a light
phase and forwarded as (19) to the drying and wax removal section
(SSRC-1). The aqueous phase thus separated (20) is sent to the Section
for Recovering Alcohols, Glycerine and Fatty Acids (SREC-1).

[0081]Alternatively, before washing the crude biodiesel can be submitted
to a step of evaporation or distillation of excess alcohol in order to
decrease the costs of dehydrating the alcohol after recovery. In this
option, the neutralized biodiesel, as (18) and (24), is sent to the
alcohol evaporation/distillation system (SEVAP-1), where all or a large
part of the alcohol content therein is removed and forwarded to the
Section for Recovering Alcohols, Glycerine and Fatty Acids (SREC-1) as
(27). After removing the alcohol, a dense phase rich in glycerine is
separated, also in the alcohol evaporation/distillation system (SEVAP-1),
and forwarded as (26) to the Section for Recovering Alcohols, Glycerine
and Fatty Acids (SREC-1). The semi purified biodiesel then passes as (25)
to the washing system (SLAV-1).

[0082]Washed biodiesel which enters the drying and wax removal section
(SSRC-1) as (19) is dried, preferably under heat and vacuum, under
pressure and temperature controlled in accordance with the type of oil or
fat used as the starting materials, followed by cooling and separation of
waxes and other high-melting point compounds.

[0083]In the case of methyl biodiesel from castor oil, simple cooling to
ambient temperature, followed by decantation for a few days, already
enables the separation of a considerable proportion of solids. The degree
of removal of wax and of other high-melting point compounds will depend
on the specification for the plugging point desired in the final product.
This product leaves the drying and wax removal section (SSRC-1) as (21)
to tank storage.

[0084]The dense phases sent to the Section for Recovering Alcohols,
Glycerine and Fatty Acids (SREC-1) as (15), (17), (20), (26) and (27)
enter this section at specific points, depending on their water contents
and the decision as to the type of recovery to be adopted, such as, for
example, mixing or treating the aqueous phases separately, recovering all
of the glycerine from the aqueous phases or treating them only for
disposal, and dehydrating the alcohol recovered or selling it as hydrated
alcohol (when the process uses ethyl alcohol), etc.

[0085]In the diagram in FIG. 2, the configuration of the Purification
Section (SP-1) is the same as in FIG. 1, with some alternative steps
added to the configuration of the Reaction Section (SR-2), as detailed
below.

[0086]The diagram in FIG. 2 presents process and equipment configurations
similar to those in FIG. 1, with the addition of alternatives intended to
minimize contamination by water of the alcohol recovered and thus
decrease the cost of purifying the alcohol recovered.

[0087]The starting materials for the process, constituted by oil or fat
(1), alcohol (2) and catalyst (3), are fed to reaction module (MR-1A) in
the ideal proportions at the ideal temperatures for the starting
materials employed. As they pass through the reaction module (MR-1A)
these materials are mixed, reacted and separated into a dense phase (5)
and light phase (4), both formed during the reaction. Simultaneously,
fresh oil or fat (12) and catalyst (13) are fed to reaction module
(MR-1B), to which is also fed (11), constituted totally or partially of
the dense phases (5), (9) and (38) from reaction modules (MR-1A) and
(MR-2) and the residual catalyst extraction system (SEXT-1). As in FIG.
1, (11) enables reuse of the catalyst in the configuration in FIG. 2.

[0088]The three are supplied to reaction module (MR-1B) regulated to the
ideal proportions and temperature, and mixed, reacted, and separated into
a dense phase, (15), and light phase, (8), both formed during the
reaction. The light phases (8) separated in reaction modules (MR-1A),
(4), and (MR-1B), (8), are then forwarded to reaction module (MR-2),
together with fresh alcohol (6) and catalyst (7). These four, previously
regulated to the ideal proportions and temperatures, are mixed, reacted,
and separated into a dense phase (9) and light phase (10) both formed
during the reaction.

[0090]The dense phase separated in reaction module (MR-2) is withdrawn as
(9), and is united with the dense phase (5) separated in reaction module
(MR-1A) and with the dense phase (38) from the residual catalyst
extraction system (SEXT-1), to give (11), which is fed to reaction module
(MR-1B).

[0091]The dense phase separated in reaction module (MR-1B) is withdrawn as
(15), and is united with the recycled dense phase (29), which is fed back
to the residual catalyst extraction system (SEXT-1) to promote extraction
of part of the excess catalyst retained in the biodiesel-rich phase (10)
leaving reaction modules (MR-2). This operation is carried out with one,
two or three theoretical stages of intimate contact between the phases
within the residual catalyst extraction system (SEXT-1).

[0092]After extraction, the biodiesel-rich phase (23) passes to the
Purification Section (SP-1), where it is subjected to the same processing
steps described in FIG. 1.

[0093]The glycerine-rich phase (28) is divided into three fractions (29),
(30) and (38).

[0094]Fraction (29) is recycled to the residual catalyst extraction system
(SEXT-1), in order to complete the inventory necessary for extraction.

[0095]Fraction (38) is united with the other fractions rich in residual
catalyst which make up (11), which supplies reaction module (MR-1B) with
recovered catalyst. The size of this fraction depends on the content of
catalyst to be recovered in the residual catalyst extraction system
(SEXT-1).

[0096]Finally, fraction (30) closes the cycle, discharging glycerine
produced within the totality of the process in the Section for Recovering
Alcohols, Glycerine and Fatty Acids (SREC-1).

[0097]Fraction (22) aids in closing the cycle by discharging into (30) the
excess dense phase not used in reaction module (MR-1B) or in the residual
catalyst extraction system (SEXT-1).

[0098]Alternatively, (15) can be rerouted to the alcohol
evaporation/distillation system (SEVAP-2) via (31), where excess alcohol
is removed and forwarded to the Section for Recovering Alcohols,
Glycerine and Fatty Acids (SREC-1) as (33). Removal of excess alcohol
gives a product rich in glycerine, which is passed as (32) to the
residual catalyst extraction system (SEXT-1) and then follows the process
flow described above.

[0099]The diagram in FIG. 3 only considers alternatives in the process for
the Purification Section (SP-2), which can be used with the
configurations of Reaction Section (SR-1) or Reaction Section (SR-2) or
with configurations traditionally adopted for reactions producing
biodiesel.

[0100]In the Purification Section (SP-2), crude biodiesel (23), which can
be produced by any process with an acid or basic catalyst, is forwarded
to a neutralization system (SN-1), where it is subjected to reaction with
a neutralizing agent (16) and separation of the dense phase (17) and
light phase (18) products of neutralization. The light phase (18), still
constituted by crude, but neutralized, biodiesel, passes to the alcohol
extraction system (SEXT-2), and the dense phase (17) is sent to the
Section for Recovering Alcohols, Glycerine and Fatty Acids (SREC-1) (not
shown).

[0101]The alcohol extraction system (SEXT-2) also receives recovered
glycerine (35) from the Section for Recovering Alcohols, Glycerine and
Fatty Acids (SREC-1), to promote extraction of part of the excess alcohol
retained in (18), thereby preventing this alcohol from entering into
contact with washing water in the washing system (SLAV-1) and becoming
hydrated. This operation is carried out in one, two, three or four
theoretical stages of intimate contact between the phases within the
alcohol extraction system (SEXT-2). The dense phase which is separated,
(36), which is rich in glycerine and alcohol with a low moisture content,
passes to the Section for Recovering Alcohols, Glycerine and Fatty Acids
(SREC-1) in the anhydrous or semi-anhydrous form.

[0102]After extraction, the biodiesel-rich phase (34) passes to the
washing system (SLAV-1), which also receives fresh water (37), the
function of which is to remove water-soluble contaminants in the
biodiesel, such as soaps, salts, alcohols, catalyst residues and
glycerine. After close contact of the two currents, counter current or
otherwise, for various stages, the biodiesel is separated as a light
phase and forwarded as (19) to the drying and wax removal section
(SSRC-1). The aqueous phase thus separated (20) is sent to the Section
for Recovering Alcohols, Glycerine and Fatty Acids (SREC-1).

[0103]Alternatively, before washing the crude biodiesel can be submitted
to a step of evaporation or distillation of excess alcohol in order to
decrease the costs of dehydrating the alcohol after recovery. In this
option, the neutralized biodiesel, as (34) and (24), is sent to the
alcohol evaporation/distillation system (SEVAP-1), where all or a large
part of the alcohol content therein is removed and forwarded to the
Section for Recovering Alcohols, Glycerine and Fatty Acids (SREC-1) (not
shown) as (27). After removing the alcohol, a dense phase rich in
glycerine is separated, also in the alcohol evaporation/distillation
system (SEVAP-1), and forwarded as (26) to the Section for Recovering
Alcohols, Glycerine and Fatty Acids (SREC-1). The semi purified biodiesel
then passes as (25) to the washing system (SLAV-1) for final washing.

[0104]Washed biodiesel which enters the drying and wax removal section
(SSRC-1) as (19) is dried, preferably under heat and vacuum, under
pressure and temperature controlled in accordance with the type of oil or
fat used as the starting materials, followed by cooling and separation of
waxes and other high-melting point compounds.

[0105]In the case of methyl biodiesel from castor oil, simple cooling to
ambient temperature, followed by decantation for a few days, enables the
separation of a considerable proportion of solids. The degree of removal
of wax and of other high-melting point compounds will depend on the
specification for the plugging point desired in the final product. This
product leaves the drying and wax removal section (SSRC-1) as (21) to
tank storage.

[0106]The dense phases (17), (20), (26), (27) and (36) sent to the Section
for Recovering Alcohols, Glycerine and Fatty Acids (SREC-1) enter this
section at specific points, depending on their water contents and the
decision as to the type of recovery to be adopted, such as, for example,
mixing or treating the aqueous phases separately, recovering all of the
glycerine from the aqueous phases or treating them only for disposal, and
dehydrating the alcohol recovered or selling it as hydrated alcohol (when
the process uses ethyl alcohol), etc.

[0107]The diagram in FIG. 4 considers an alternative process for the
Purification Section (SP-3) similar to that in FIG. 3, differing only in
inverting the sequence of the neutralization system (SN-1) and the
alcohol extraction system (SEXT-2).

[0108]This purification flow can also be used with the configurations of
Reaction Section (SR-1) or Reaction Section (SR-2) or with configurations
traditionally adopted for reactions producing biodiesel.

[0109]In the Purification Section (SP-3), crude biodiesel (23), which can
be produced by any process with an acid or basic catalyst, is initially
sent to the alcohol extraction system (SEXT-2), which also receives
recovered glycerine (35) from the Section for Recovering Alcohols,
Glycerine and Fatty Acids (SREC-1), to promote extraction of part of the
excess alcohol retained in (23), thereby preventing this alcohol from
entering into contact with washing water in the washing system (SLAV-1)
and becoming hydrated. This operation is carried out in one, two, three
or four theoretical stages of intimate contact between the phases within
the alcohol extraction system (SEXT-2).

[0110]The dense phase separated, rich in glycerine and alcohol with a low
moisture content, is sent to the Section for Recovering Alcohols,
Glycerine and Fatty Acids (SREC-1) (not shown) as (36), where the alcohol
is recovered in anhydrous or semi-anhydrous form.

[0111]After extraction, phase (34), rich is biodiesel, is sent to the
neutralization system (SN-1), where it is subjected to reaction with a
neutralizing agent (16), and separation of the dense phase (17) and light
phase (18) products of neutralization. The light phase, still constituted
by crude, but neutralized, biodiesel with a lower alcohol content, passes
to the washing system (SLAV-1) as (18), and the dense phase passes to the
Section for Recovering Alcohols, Glycerine and Fatty Acids (SREC-1) as
(17). From this point on, the process is the same as in FIG. 3.

[0112]The concept of the invention as described in the present
specifications also includes the following additional observations.

[0113]In addition to reusing the catalyst contained in the dense phases
separated after the various reaction steps, the present invention also
offers the alternative of additional recovery of the catalyst by
extracting the light phase flowing from the last reaction step with the
dense phase flowing from the reactor, which operates without adding fresh
catalyst.

[0114]Alternatively, the dense phase used for extraction can be
pre-evaporated to remove excess alcohol, improving its capacity for
extraction and decreasing the alcohol content of the light phase, which
is passed to the purification steps.

[0115]The final washing of the biodiesel is performed using fresh water,
which can be in counter current (in order to minimize consumption of
water).

[0116]When the catalyst used in the transesterification reaction is of the
basic type, the water can be pure or have a controlled pH in the range 1
to 7, and preferably between 3 and 7, and more preferably between 3 and
5.

[0117]The ideal number of washing stages depends on the type and purity of
the oil, of the catalyst, of the alcohol, of the process conditions, of
the route chosen for removing the excess alcohol, and the efficiency of
removal and neutralization of excess catalyst. Typically this number
varies from 1 to 7 stages for counter current washing--whatever is
necessary and sufficient in order to remove the residual glycerine and
soaps.

[0118]In addition, before washing with water the present invention allows
for extraction of excess alcohol, using the glycerine leaving the system
for recovering alcohols, glycerine and fatty acids. After the extraction,
the biodiesel is passed to the normal washing steps and the glycerine
returns to the system for recovering alcohols, thereby minimizing
hydration of the alcohol, which occurs during washing of the biodiesel
with water.

[0119]Also alternatively, before washing, whether or not it has been
extracted with glycerine, the biodiesel can be submitted to preliminary
evaporation in order to increase recovery of alcohol with a low water
content.

Patent applications by Jose Antonio Vidal Vieira, Rio De Janeiro BR

Patent applications by Michele Sabba Da Silva Lima, Rio De Janeiro BR

Patent applications in class The single bonded oxygen is bonded directly to an additional carbon, which carbon may be single bonded to any element but may be multiple bonded only to carbon (i.e., carboxylic acid esters)

Patent applications in all subclasses The single bonded oxygen is bonded directly to an additional carbon, which carbon may be single bonded to any element but may be multiple bonded only to carbon (i.e., carboxylic acid esters)